Substituted pyrazolylpyrazole derivative and use of same as herbicide

ABSTRACT

Provided is a compound capable of effectively control worst weeds of higher leaf stages that present practical problems. A specific pyrazolylpyrazole derivative of formula (I) is disclosed that is able to solve the above-mentioned problems.

TECHNICAL FIELD

The present invention relates to a substituted pyrazolylpyrazolederivative and the use of that compound as a herbicide.

BACKGROUND ART

Numerous herbicides have recently come to be used in the cultivation ofagricultural crops, and have contributed to reduced labor for farmersand improved productivity of agricultural crops. Numerous herbicides arealso used practically in the cultivation of field and paddy rice.

However, there is considerable diversity in the species of weeds, thegermination and growth periods of each species of weed are not uniform,and the growth of perennial weeds extends over a long period of time.Consequently, it is extremely difficult to control all weeds with asingle spraying of herbicide.

Early to mid-term one-shot herbicides have been shown to be effectivefor paddy rice by treating during the second to third leaf stage ofpaddy weeds (generic term for Echinochloa oryzicola, Echinochloacrus-galli var. crus-galli, Echinochloa crus-galli var. formosensis,Echinochloa crus-galli var. praticola and Echinochloa crus-galli var.caudata), and major weeds can be controlled by a single treatment (seeNon-Patent Document 1). However, it is extremely difficult to controlpaddy weeds that have grown to the 3.5 leaf stage or more with early tomid-term one-shot herbicides currently in practical use, and the controlof paddy weeds in the third leaf stage and control of paddy weeds in the3.5 leaf stage are technically completely different.

Moreover, maintaining herbicidal effects (or residual activities) over along period of time is important in terms of reducing spraying ofagricultural chemicals, saving on labor and curtailing costs, and isconsidered to be an essential area of performance for early to mid-termone-shot herbicides.

In addition, acetolactate synthase (ALS) inhibitors have come to bewidely used in recent years, and weeds exhibiting resistance to ALSinhibitors have become a problem. There are few herbicides demonstratingadequate efficacy against ALS inhibitor-resistant biotypes of theperennials of Sagittaria trifolia and Sagittaria pygmeae. In addition,examples of perennial weeds that have caused problems in recent yearsinclude Eleocharis kuroguwai, Scirpus planiculmis and Scirpusnipponicus, while examples of annuals include Aeschynomene indcica,Leptochloa chinensis and Murdannia keisak, and there are few herbicidesthat demonstrate adequate efficacy against these difficult-to-controlweeds.

On the other hand, numerous pyrazole derivatives are used practically asherbicides, and although pyrazole derivatives such as4-(2,4-dichlorobenzoyl)-1,3-dimethyl-5-pyrazolyl p-toluenesulfonate(common name: “Pyrazolate”),2-[4-(2,4-dichlorobenzoyl)-1,3-dimethylpyrazol-5-yloxy]acetophenone(common name: “Pyrazoxyfen”) or2-[4-(2,4-dichloro-m-toluoyl)-1,3-dimethylpyrazol-5-yloxy]-4′-methylacetophenone(common name: “Benzofenap”) are widely used, their registeredapplication range for paddy weeds in Japan when used alone is up to the1.5 leaf stage, and although these pyrazole derivatives are effectiveagainst a wide range of weeds, the efficacy thereof is not alwaysadequate against paddy weeds of higher leaf stages.

In addition, although Compound 73 of Example 4 described in WO 94/08999in the form of 1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-5-[methyl(prop-2-ynyl)amino]pyrazole-4-carbonitrile(common name: “Pyraclonil”) is effective against a wide range of weeds,its efficacy against paddy weeds of higher leaf stages is inadequate,and the registered application range in Japan against paddy weeds whenusing this herbicide alone is up to the 1.5 leaf stage.

Moreover, although WO 94/08999 also discloses compounds that demonstrateherbicidal effects by treating weeds that grow on farmland before andafter growth, since there is no description regarding leaf stage, itcannot be said that these compounds have adequate effects against weedsof higher leaf stages. In addition, although isopropyl ammoniumN-(phosphonomethyl) glycinate (common name: “Glyphosate IsopropylamineSalt”), for example, is widely used as a herbicide that demonstrates awide range of effects against farmland weeds, problems have arisen inrecent years regarding its efficacy against resistant weeds.

In addition, there has recently been growing concern over pollution ofgroundwater and rivers by pesticides. Consequently, there is a need forthe development of herbicides that minimize effects on the environmentsuch as by lowering the risk of runoff of active ingredients tolocations other than locations of their intended application.

CITATION LIST

Patent Literature Document

-   Patent Document 1: WO 94/08999

Non-Patent Literature Document

-   Non-Patent Document 1: “Suiden Zasso no Seitai to Sono    Bojo—Suitosaku no Zasso to Josozai Kaisetsu (Ecology of Paddy Weeds    and their Control—Explanation of Weeds of Rice Paddy Crops and    Herbicide)”, p. 159

SUMMARY OF THE INVENTION Technical Problem

An object of the present invention is to provide a compound that hassuperior characteristics as an herbicide ingredient, such as having awide herbicidal spectrum including weeds that are resistant to existingherbicides, being able to control worst weeds of higher leaf stages thatpresent practical problems, and not causing phytotoxicity to crops suchas paddy rice.

Solution to Problem

As a result of conducting extensive studies to achieve theaforementioned object, the inventors of the present invention found thata pyrazolylpyrazole derivative having a specific chemical structureespecially exhibits a broad herbicidal spectrum over a long period oftime, demonstrates superior herbicidal efficacy against worst weeds ofhigher leaf stages, and has adequate safety with respect to cultivatedcrops, thereby leading to completion of the present invention on thebasis of these findings. Thus, the present invention, provides apyrazolylpyrazole derivative in the form of a compound represented bythe following formula (I):

In the above formula,

R¹ represents a chlorine atom or bromine atom,

R² represents a cyano group or nitro group,

R³ represents a C₁-C₆ alkyl group (which may be substituted with one ormore halogen atoms depending on the case), fluorine atom, chlorine atomor bromine atom, and

a represents 3 to 5.

Preferably,

in formula (I),

R¹ represents a chlorine atom,

R² represents a cyano group,

R³ represents a C₁-C₄ alkyl group (which may be substituted with one ormore halogen atoms depending on the case), chlorine atom or bromineatom, and

a represents 4.

In the present description:

the mark “C_(a)-C_(b)” which is followed by a substituent means that thesubstituent has a to b carbon atoms.

Fluorine, chlorine, bromine and iodine atoms are included in “halogenatoms”.

“Alkyl” as referring to a group per se or a moiety of a group can belinear or branched, and although there are no limitations thereon,examples thereof include methyl, ethyl, n- or isopropyl, n-, iso-, sec-or tert-butyl, n-pentyl and n-hexyl groups, and each is selected withina range of the specified number of carbon atoms thereof.

In the case of the “alkyl group”, at least one hydrogen atom containedin these groups may be substituted with a halogen atom, and althoughthere are no limitations thereon, examples thereof when using theexample of an alkyl group include chloromethyl, dichloromethyl,trifluoromethyl, chloroethyl, dichloroethyl, trifluoroethyl,tetrafluoropropyl, bromoethyl, bromopropyl, chlorobutyl, chlorohexyl andperfluorohexyl groups, and each of these is selected within a range ofthe specified number of carbon atoms thereof.

In the case where the aforementioned group or moiety is substituted witha plurality of halogen atoms, that group can be substituted with morethan one halogen atoms that are the same or different.

In all of the formulas listed below, substituents and symbols have thesame meanings as defined for formula (1) unless specifically definedotherwise. The compounds of formula (I) provided by the presentinvention in which R³ is a hydrogen atom can easily be synthesized by anamidation reaction from a compound represented by formula (II).

The compound of formula (II) can be synthesized fromtetrahydro-2H-pyran-2-ylidene acetonitrile or 5-chlorovaleryl chlorideaccording to the methods described in WO 93/10100 and WO 94/08999.

The amidation reaction of the compound of formula (II) per se can becarried out with reference to known reaction conditions (see, forexample, WO 94/08999 and Tetrahedron Lett., 32, 4019 (1991)).

The compound of formula (I) provided by the present invention hassuperior herbicidal efficacy and is useful as a herbicide as is clearfrom the results of the herbicidal activity tests described in TestExamples 1 to 4 to be subsequently described.

The compound of formula (I) of the present invention has activityagainst numerous types of crop weeds and non-crop weeds. Examples ofcultivated plants include gramineous plants such as rice, wheat, barley,corn, oats or sorghum, broadleaf crops such as soybeans, cotton, beets,sunflowers or rapeseed, fruit trees, vegetables such as fruitvegetables, root vegetables or leafy vegetables, and grasses, and thecompound of formula (I) can be used for the cultivation thereof.

The compound of the present invention has herbicidal efficacy againstthe various weeds listed below that cause problems in rice paddies inany of the treatment methods of soil treatment in an irrigated orunirrigated state, soil incorporation treatment and foliar treatment.Although the following lists examples thereof, these weeds are notlimited to the following examples.

Examples of paddy weeds that can be controlled by the compound offormula (I) of the present invention include Alismataceous weeds such asAlisma canaliculatum, Sagittaria trifolia or Sagittaria pygmaea,Cyperaceous weeds such as Cyperus difformis, Cyperus serotinus, Scirpusjuncoides, Eleocharis kuroguwai, Scirpus planiculmis or Scirpusnipponicus, Scrophulariaceous weeds such as Lindernia procumbens,Lindernia dubia subsp. dubia or Lindernia dubia, Pontederiaceous weedssuch as Monochoria vaginalis or Monochoria korsakowii, Potamogetonaceousweeds such as Potamogeton distinctus, Lythraceous weeds such as Rotalaindica or Ammannia multiflora, Asteraceous weeds such as Bidenstripartita or Bidens frondosa, Leguminoseous weeds such as Aeschynomeneindica, Commelinaceous weeds such as Murdannia keisak, and Gramineousweeds such as Echinochloa oryzicola, Echinochloa crus-galli var.crus-galli, Echinochloa crus-galli var. formosensis, Echinochloacrus-galli var. praticola, Echinochloa crus-galli var. caudata,Leptochloa chinensis, Leersia japonica, Paspalum distichum or Leersiaoryzoides.

In addition, the compound of the present invention has herbicidalefficacy against the various weeds listed below that cause problems infield land and non-crop land in any of the treatment methods of soiltreatment, soil incorporation treatment and foliar treatment. Althoughthe following lists examples thereof, these weeds are not limited to thefollowing examples.

Examples thereof include broadleaf weeds, including Solanaceous weedssuch as Solanum nigrum or Datura stramonium, Malvaceous weeds such asAbutilon avicennae, Sida spinosa or Convolvulus arvensis,Convolvulaceous weeds such as Ipomoea pupurea, Amaranthaceous weeds suchas Amaranthus lividus, Amaranthus retroflexus, Amaranthus palmeri orAmaranthus tuberculatus, Asteraceous weeds such as Xanthium strumarium,Ambrosia artemisiilifolia, Galinsoga ciliata, Cirasium arvense, Seneciovulgaris, Stenactis annuus, Galinsoga parviflora, Sonchus arvensis,Sonchus oleraceus or Matricaria indora, Brassicaceous weeds such asRorippa indica, Sinapis arvensis, Capsella bursa-pastoris or Thlaspiarvense, Polygonaceous weeds such as Persicaria longiseta, Fallopiaconvolvulus, Polygonum aviculare var. condensatum, Polygonum avicularevar. monospeliense, Polygonum persicaria, Persicaria lapathifolia var.incana or Persicaria lapathifolia var. lapathifolia, Portulacaceousweeds such as Portulaca oleracea, Chenopodiaceous weeds such asChenopodium album, Chenopodium ficifolium, Kochia scoparia or Atriplexpatula, Caryophyllaceous weeds such as Stellaria media,Scrophulariaceous weeds such as Veronica persica, Commelinaceous weedssuch as Commelina communis, Lamiaceous weeds such as Lamiumamplexicaule, Lamium purpureum or Galeopsis tetrahit, Euphorbiaceousweeds such as Euphorbia supina or Euphorbia maculata, Rubiaceous weedssuch as Galium spurium, Galium spurium var. Echinospermon, Rubia argyior Galium aparine, Violaceous weeds such as Viola mandshurica or Violaarvensis, Boraginaceous weeds such as Myosotis arvensis, andLeguminoseous weeds such as Sesbania exaltata or Cassia obfusitolia, andGramineous weeds such as Sorghum bicolor, Panicum dichotomiflorum,Sorghum halepense, Echinochloa crus-galli var. crus-galli, Digitariaciliaris, Avena fatua, Eleusine indica, Setaria viridis, Alopecurusaequalis, Poa annua, Agropyron repens, Cynodon dactylon, Digitariasanguinalis, Setaria pumila or Alopecurus myosuroides, and Cyperaceousweeds such as Cyperus rotundus.

Moreover, the compound of the present invention is also able to controla wide range of weeds growing in mowed swaths, fallow land, orchards,grasslands, lawn grass plots, train line caps, vacant land and forestland, or on farm roads, causeways and other non-crop land.

Moreover, the compound of formula (I) of the present invention does notdemonstrate phytotoxicity that becomes a problem for paddy rice in thecase of any cultivation method such as direct seeding cultivation ortransplantation cultivation of paddy rice.

The compound of formula (I) of the present invention can be appliedbefore or after plant germination and can be mixed into soil beforeseeding.

Although the dosage of the compound of formula (I) of the presentinvention can be varied over a wide range corresponding to the type ofcompound, type of target plant, application window, location ofapplication, properties of desired effects and the like, and as ageneral reference thereof, the dosage can be within the range of about0.01 g to 100 g, and preferably about 0.1 g to 10 g, as the amount ofactive compound per are.

Although the compound of formula (I) of the present invention can beused alone, a formulation assistant and the like is normallyincorporated in the compound of formula (I) in accordance with ordinarymethods, and although there are no limitations thereon, it is preferablyformulated and used in any arbitrary drug form such as a dustablepowder, emulsifiable concentrate, oil miscible liquid, solubilizingagent, suspo-emulsion, fine granule, aerosol spray, less drifting dust,micro granules fine, fine grains F, granules, wettable powder, waterdispersible granules, flowable concentrate, throw-in types (Jumbo),tablets, paste, emulsion in oil, water soluble powder, water solublegranules, soluble concentration or capsule suspension.

There are no limitations on formulation assistants able to be used forformulation, and examples include solid vehicles, liquid vehicles,binders, thickeners, surfactants, anti-freezing agents andpreservatives.

Examples of solid vehicles include, but are not limited to, talc,bentonite, montmorillonite, clay, kaolin, calcium carbonate, sodiumcarbonate, sodium bicarbonate, mirabilite, zeolite, starch, acidic clay,diatomaceous earth, chaoite, vermiculite, slaked lime, vegetable powder,alumina, activated carbon, sugars, hollow glass, silica sand, ammoniumsulfate and urea.

Examples of liquid vehicles include, but are not limited to,hydrocarbons (such as kerosene or mineral oil), aromatic hydrocarbons(such as toluene, xylene, dimethyl naphthalene or phenyl xylyl ethane),chlorinated hydrocarbons (such as chloroform or carbon tetrachloride),ethers (such as dioxane or tetrahydrofuran), ketones (such as acetone,cyclohexanone or isophorone), esters (such as ethyl acetate, ethyleneglycol acetate or dibutyl maleate), alcohols (such as methanol,n-hexanol or ethylene glycol), polar solvents (such asN,N-dimethylformamide, dimethylsulfoxide or N-methylpyrrolidone) andwater.

Examples of binders and thickeners include, but are not limited to,dextrin, sodium salts of carboxymethyl cellulose, polycarboxylicacid-based polymer compounds, polyvinylpyrrolidone, polyvinyl alcohol,sodium lignin sulfonate, calcium lignin sulfonate, sodium polyacrylate,gum arabic, sodium alginate, mannitol, sorbitol, bentonite-based mineralmatter, polyacrylic acid and derivatives thereof, chaoite and naturalsugar derivatives (such as xanthan gum or guar gum).

Examples of surfactants include, but are not limited to, anionicsurfactants such as fatty acid salts, benzoates, alkylsulfosuccinates,dialkylsulfosuccinates, polycarboxylates, alkyl sulfate ester salts,alkyl sulfates, alkyl aryl sulfates, alkyl diglycol ether sulfates,alcohol sulfate ester salts, alkyl sulfonates, alkyl aryl sulfonates,aryl sulfonates, lignin sulfonates, alkyl diphenyl ether disulfonates,polystyrene sulfonates, alkyl phosphate ester salts, alkyl arylphosphates, styryl aryl phosphates, polyoxyethylene alkyl ether sulfateester salts, polyoxyethylene alkyl aryl ether sulfates, polyoxyethylenealkyl aryl ether sulfate ester salts, polyoxyethylene alkyl etherphosphates, polyoxyethylene alkyl aryl phosphate ester salts or salts ofnaphthalene sulfonate-formalin condensates, and nonionic surfactantssuch as sorbitan fatty acid esters, glycerin fatty acid esters, fattyacid polyglycerides, fatty acid alcohol polyglycol ethers, acetyleneglycol, acetylene alcohol, oxyalkylene block polymers, polyoxyethylenealkyl ethers, polyoxyethylene alkyl aryl ethers, polyoxyethylene styrylaryl ethers, polyoxyethylene glycol alkyl ethers, polyoxyethylene fattyacid esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethyleneglycerin fatty acid esters, polyoxyethylene hydrogenated castor oil orpolyoxypropylene fatty acid esters.

Examples of anti-freezing agents include, but are not limited to,ethylene glycol, diethylene glycol, propylene glycol and glycerin.

Examples of preservatives include, but are not limited to, benzoic acid,sodium benzoate, methyl paraoxybenzoate, butyl paraoxybenzoate,isopropyl methyl phenol, benzalkonium chloride, chlorhexidinehydrochloride, aqueous hydrogen peroxide, chlorhexidine gluconate,salicylic acid, sodium salicylate, zinc pyrithione, sorbic acid,potassium sorbate, dehydroacetic acid, sodium dehydroacetate,phenoxyethanol, isothiazoline derivatives such as5-chloro-2-methyl-4-isothiazolin-3-one or 2-methyl-4-isothiazolin-3-one,2-bromo-2-nitropropane-1,3-diol and salicylic acid derivatives.

The previously mentioned solid vehicles, liquid vehicles, binders,thickeners, surfactants, anti-freezing agents and preservatives can eachbe used alone or in a suitable combination thereof corresponding to thepurpose of use and the like.

Although the incorporated ratio of the compound of formula (I) of thepresent invention with respect to the total herbicide composition of thepresent invention can be increased or decreased as necessary and thereare no particular limitations thereon, it is normally about 0.01% byweight to 90% by weight, and for example, in the case of being in theform of a dustable powder or granules, is preferably about 0.1% byweight to 50% by weight and more preferably about 0.5% by weight to 10%by weight, while in the case of being in the form of an emulsifiableconcentrate, wettable powder or water dispersible granules, ispreferably about 0.1% by weight to 90% by weight and more preferablyabout 0.5% by weight to 50% by weight.

These preparations can be provided for use in various types ofapplications by diluting to a suitable concentration as necessaryfollowed by spraying or applying directly to plant foliage, soil or thesurface of a rice paddy and the like.

The following provides an explanation of the present invention throughexamples thereof.

EXAMPLES Example 1: Method for the Synthesis ofN-(1-(3-chloro-4,5,6,7-tetrahydropyrazolo[1,5-a]pyridin-2-yl)-4-cyanopyrazol-5-yl) Heptylamide (Compound 1)

Acetonitrile (200 ml) was added to5-amino-1-(3-chloro-4,5,6,7-tetrahydropyrazolo(1,5-a)pyridin-2-yl)pyrazole-4-carbonitrile(36.8 g) followed by slowly dropping in heptanoyl chloride (25.0 g) andheating to reflux for 1 day. Following completion of the reaction, waterwas added to the reaction solution followed by extraction with ethylacetate. After washing with saturated aqueous sodium bicarbonatesolution and drying with sodium sulfate, the solvent was distilled offunder reduced pressure. Hexane (100 ml) and isopropyl ether (50 ml) wereadded to the resulting crude product followed by stirring for 3 hours inan ice bath. The solid that precipitated was washed with isopropyl etherto obtain the desired compound (35.2 g).

The starting material in the form of the compound of formula (II) wassynthesized in accordance with WO 93/101.00 and WO 94/08999.

The examples listed in the following tables can be synthesized by thesame manner as the above-mentioned methods or obtained in the samemanner as the above-mentioned methods.

[Table 1]

TABLE 1

Refractive Compound R¹ R² R³ a mp index (° C.)  1 Cl CN Et 4 56-79  2 ClCN Me 4 108-109  3 Cl CN propyl 4 78-99  4 Cl CN butyl 4  92-128  5 ClCN pentyl 4 92-97  6 Cl CN heptyl 4 82-99  7 Cl CN Cl 4 125-126  8 Cl CNF 4  9 Cl CN Br 4 10 Cl NO₂ Me 4 11 Cl NO₂ Et 4 12 Cl NO₂ propyl 4 13 BrCN Me 4

Preparation Examples

1. Dustable Powder

Compound of formula (I) 10 parts by weight Talc 90 parts by weight

A dustable powder is obtained by mixing the above components and finelycrushing with a hammer mill.

2. Wettable Powder

Compound of formula (I)   10 parts by weight Polyoxyethylene alkyl arylether sulfate 22.5 parts by weight White carbon 67.5 parts by weight

A wettable powder is obtained by mixing the above components and finelycrushing the mixture with a hammer mill.

3. Flowable Concentrate

Compound of formula (I) 10 parts by weight Polyoxyethylene alkyl etherphosphate 10 parts by weight Bentonite  5 parts by weight Ethyleneglycol  5 parts by weight Water 70 parts by weight

A flowable concentrate is obtained by mixing the above components andcrushing using a wet pulverizer.

4. Emulsifiable Concentrate

Compound of formula (I) 15 parts by weight Ethoxylated nonylphenol 10parts by weight Cyclohexanone 75 parts by weight

An emulsifiable concentrate is obtained by mixing the above components.

5. Granules

Compound of formula (I) 5 parts by weight Calcium lignin sulfonate 3parts by weight Polycarboxylate 3 parts by weight Calcium carbonate 89parts by weight 

The above components are mixed followed by adding water, kneading,extruding and granulating. Subsequently, granules are obtained by dryingfollowed by sizing.

Biological Testing Examples

1. Paddy Herbicidal Activity Test

Rice paddy soil was filled into a 1/10000 are pot followed by theaddition of suitable amounts of water and chemical fertilizer, kneading,seeding with Echinochloa crus-galli, Monochoria vaginalis and Scirpusjuncoides and maintaining in an irrigated state at a water depth of 3cm.

Wettable powders of Target Compound (I) shown in Table 1 prepared incompliance with the preparation examples were diluted with a suitableamount of water, rice plants in the 2.0 leaf stage were transplantedduring 3.5 leaf stage of Echinochloa crus-galli, and treated by droppingin chemical in the prescribed amount per 10 are using a pipette.

After treating for 30 days in a glass greenhouse at an averageatmospheric temperature of 30° C., the herbicidal efficacy thereof wasinvestigated.

Evaluation of herbicidal efficacy was carried out by comparing growthinhibition rate (%) with an untreated group, while evaluation ofphytotoxicity was carried out by comparing growth inhibition rate (%)with the state of a complete eradication group, and were evaluated at 11levels indicated below.

0 (exponent): 0% to less than 10% (growth inhibition rate)

1: 10% to less than 20%

2: 20% to less than 30%

3: 30% to less than 40%

4: 40% to less than 50%

5: 50% to less than 60%

6: 60% to less than 70%

7: 70% to less than 80%

8: 80% to less than 90%

9: 90% to less than 100%

10: 100%

The results are shown in Table 2.

Control agent 1.37 (described in WO 94/08999)

Control agent 4.188 (described in WO 94/08999)

Control agent 4.191 (described in WO 94/08999)

TABLE 2 5 g^(a.i.)/10a 1 g^(a.i.)/10a Echinochloa Scirpus MonochoriaOryza Echinochloa Scirpus Monochoria Oryza Compound crus-galli juncoidesvaginalis sativa crus-galli juncoides vaginalis sativa 1 10 10 10 1 10 910 1 2 10 10 10 2 10 9 10 1 3 10 10 10 1 10 10 10 1 4 10 10 10 1 9 10 100 7 10 10 10 2 9 9 9 1 1.37 3 2 4 2 3 1 2 2 4.188 3 1 3 2 2 0 3 2 4.1912 1 2 1 2 0 2 1

2. Farming Soil Treatment Test

Field soil was filled into a 1/6000 are pot followed by seeding withDigitaria ciliaris, Chenopodium album and Amaranthus retroflexus andcovering with soil.

Wettable powders of compounds of formula (I) shown in Table 1 preparedin compliance with the preparation examples were diluted with water tothe prescribed amount of chemical and uniformly sprayed onto each soilsurface layer using 100 liters of sprayed water per 10 are prior to weedgrowth following seeding.

After treating for 30 days in a glass greenhouse at an averageatmospheric temperature of 30° C., the herbicidal efficacy thereof wasinvestigated.

Evaluation of herbicidal efficacy was carried out in the same manner asthe above-mentioned Test Example 1,

The results are shown in Table 3.

TABLE 3 10 g^(a.i.)/10a 5 g^(a.i.)/10a Digitaria Chenopodium AmaranthusDigitaria Chenopodium Amaranthus Compound ciliaris album retroflexusciliaris alubum retroflexus 1 10 10 10 10 9 10 2 10 10 10 10 9 10 3 1010 10 10 10 10 4 9 10 9 9 10 9 7 9 10 9 9 9 9 1.37 4 5 6 3 4 5 4.188 1 34 0 2 4 4.191 0 3 3 0 3 2

3. Weed Foliar Treatment Test

Soil was filled into a 1/6000 are pot followed by seeding with Digitariaciliaris, Chenopodium album and Amaranthus retroflexus, covering withsoil, and cultivating in a glass greenhouse at an average atmospherictemperature of 25° C.

Wettable powders of Target Compound (I) shown in Table 1 prepared incompliance with the preparation examples were diluted with water to theprescribed amount of chemical and uniformly sprayed onto the weeds using150 liters of sprayed water per 10 are when Digitaria ciliaris had grownto the 1.0 to 2.0 leaf stage.

After treating for 3 weeks in a glass greenhouse at an averageatmospheric temperature of 25° C., the herbicidal efficacy thereof wasinvestigated.

Evaluation of herbicidal efficacy was carried out in the same manner asthe above-mentioned Test Example 1.

The results are shown in Table 4.

TABLE 4 10 g^(a.i.)/10a 5 g^(a.i.)/10a Digitaria Chenopodium AmaranthusDigitaria Chenopodium Amaranthus Compound ciliaris album retroflexusciliaris alubum retroflexus 1 10 10 10 10 10 10 2 10 10 10 10 10 10 3 1010 10 10 10 10 4 10 10 10 9 10 10 7 9 10 10 9 10 10 1.37 4 5 7 3 4 64.188 2 5 5 1 3 4 4.191 0 2 5 0 3 4

4. Weed Foliar Treatment Test

Field soil was filled into a 1/4500 are pot followed by seeding withDigitaria ciliaris and Galinsoga parviflora, covering with soil andcultivating in a glass greenhouse at an average atmospheric temperatureof 25° C.

Wettable powders of Target Compound (I) shown in Table 1 prepared incompliance with the preparation examples were diluted with water to theprescribed amount of chemical and uniformly sprayed onto the weeds using100 liters of sprayed water per 10 are when Digitaria ciliaris had grownto the 4.0 to 5.0 leaf stage (plant height: 10 cm to 15 cm).

After treating for 20 days in a glass greenhouse at an averageatmospheric temperature of 25° C., the herbicidal efficacy thereof wasinvestigated.

Evaluation of herbicidal efficacy was carried out in the same manner asthe above-mentioned Test Example 1.

The results are shown in Table 5.

TABLE 5 10 g^(a.i.)/10a Compound Digitaria ciliaris Galinsoga parviflora1 10 10 2 10 10 3 10 10 4 10 10 5 9 10 7 9 10 1.37 2 4 4.188 0 4 4.191 03

INDUSTRIAL APPLICABILITY

According to the present invention, the compound for formula (I) of thepresent invention is useful as a herbicide against harmful plants sinceit has superior herbicidal efficacy against undesirable plants.

1. A compound represented by the following formula (I):

wherein, R¹ represents a chlorine atom or bromine atom, R² represents acyano group or nitro group, R³ represents a C₁-C₆ alkyl group which maybe substituted with one or more halogen atoms depending on the case,fluorine atom, chlorine atom or bromine atom, and a represents 3 to 5.2. The compound according to claim 1, wherein R¹ represents a chlorineatom, R² represents a cyano group, R³ represents a C₁-C₄ alkyl groupwhich may be substituted with one or more halogen atoms depending on thecase, chlorine atom or bromine atom, and a represents
 4. 3. A herbicidecomposition containing a herbicidally effective amount of at least onecompound according to claim
 1. 4. The herbicide composition according toclaim 3, further containing a formulation assistant.
 5. A method forcontrolling undesirable plants, said method comprising the step ofapplying an effective amount of at least one compound according to claim1 to an undesirable plant or the location of the undesirable plant. 6.(canceled)
 7. (canceled)
 8. A herbicide composition containing aherbicidally effective amount of at least one compound according toclaim
 2. 9. The herbicide composition according to claim 8, furthercontaining a formulation assistant.
 10. A method for controllingundesirable plants, said method comprising the step of applying aneffective amount of at least one compound according to claim 2 to anundesirable plant or the location of the undesirable plant.
 11. A methodfor controlling undesirable plants, said method comprising the step ofapplying an effective amount of the herbicide composition according toclaim 3 to an undesirable plant or the location of the undesirableplant.
 12. A method for controlling undesirable plants, said methodcomprising the step of applying an effective amount of the herbicidecomposition according to claim 8 to an undesirable plant or the locationof the undesirable plant.
 13. A method for controlling undesirableplants, said method comprising the step of applying an effective amountof the herbicide composition according to claim 4 to an undesirableplant or the location of the undesirable plant.
 14. A method forcontrolling undesirable plants, said method comprising the step ofapplying an effective amount of the herbicide composition according toclaim 9 to an undesirable plant or the location of the undesirableplant.